You can use ContextMenu plugin (ContextMenu::Main, Main menu->Enable) and Main menu->Plugins->Special characters.
Also can use ToolBar plugin (ToolBar::Main) for display tool bar with the appropriate icon.

#2
Turn on ToolBar plugin (ToolBar::Main). There you have three icons:
- "Split into four panes",
- "Split vertically",
- "Split horizontally".

Using ContextMenu plugin, you can add these commands to the main menu.
Hotkeys plugin (Hotkeys::Main) allows you to add the shortcut keys.